It is known that voice discontinuity during a phone call is generally due to network channel problems such as packet loss or delay. However, the voice discontinuity can also be observed in the far-end talker (FET) signal when the near-end talker (NET) is surrounded by noisy environment.
Typically, an acoustic echo canceler (AEC) employed in a telecommunication system includes an adaptive filter. When a double talk event between a near-end talker and a far-end talker is detected by a double talk detector in the telecommunication system, the double talk detector usually freezes the adaptive filter in order to update no more signals in the double talk event. Since most of the AEC-equipped products are designed to substantially support half-duplex operating mode, voice discontinuity occurs when a double talk event is detected. In noisy environment, a double talk event can be caused by a background noise around a near-end talker, even in case where the near-end talker does not speak, which induces a voice discontinuity. In such cases, the voice discontinuity is more of the problems caused by background noise of nearby environment rather than the network channel problems.
To evaluate sound quality of a telecommunication system, it is necessary to identify the quality degradation due to ambient background noise and distinguish it from the quality degradation due to network channel. Also, the objective quality of experience (QoE) measure is necessary to evaluate the sound quality of the background noise environment.